Atomic Mass - Integrated Biology And skills for success in science

Lecture Presentations
for Integrated Biology and Skills for Success in Science
Banks, Montoya, Johns, & Eveslage
Chapter #2 Lecture – pp 12-29
Science, Atoms, Elements, & Subatomic Particles
Guiding Principles for the Course
 Looking at seemingly simple things deeply
 Conceptual understanding
 Practical Applications
 Contextualized
Chapter #2 – Learning Objectives
 By the end of the lecture today, students will be able to:
 List and define the typical stages in the scientific method.
 Compare and contrast inductive versus deductive reasoning.
 Compare and contrast mass versus weight as scientific values
 Determine the mass of an atom when given the subatomic particles.
 Define and describe chemistry terms such as element, subatomic
particle, proton, neutron, electron, atomic number and atomic mass.
 Define isotopes and describe differences between isotopes of an
element.
 List the most abundant elements found in the human body.
 Distinguish the role of valence electrons in chemical reactions
 Identify and describe any general trends that can be observed in the
periodic table of elements including but not limited to atomic mass,
ionization energies, and electronegativity values.
Scientific Method
 The Scientific Method involves a
series of steps that are used to
investigate a natural
occurrence
 It is important to develop a deep
understanding of this approach
to science as it is a universal way
of looking at problems,
situations, and phenomena in
nature
 Please become familiar with
the flowchart presented here
and in your text
Deductive vs. Inductive Logic
 It is very important to define the differences between the two major
types of logic that will be used to drive the scientific method in your
future observations of nature
 Deductive logic starts with a statement believed to be true and then goes on to
predict what facts would also have to be true to be compatible with that statement
 In contrast, inductive logic involves taking observations of facts and creating a new
theory that is compatible with those observations of facts
Control vs. Comparative Experiments
 There are two main types of experiments used in science: The
Controlled Experiment and The Comparative Experiment
 The purpose of a controlled science experiment is to find out what
happens to something if you change something else while you keep all
other things unchanged
 In a controlled experiment you can test only one independent variable
 This means that you can change only one condition in your experiment
 The purpose of a comparative experiment is to compare the effect of
two or more different things on something
 In a comparative experiment you can test the effect of a few independent
variables but not in the same experimental group where also only one
independent variable is allowed as in the case of a controlled experiment
What is Biochemistry??
 Life is all about the multitude of biochemical
reactions that take place all day every day
 Each part of every living organism is
biochemically connected
 Biochemistry is defined as the study of life on a
molecular level
 Biochemistry covers the biochemical bonds
linking atoms to form simple molecular
structures and larger structures like DNA, which
holds genetic information which flows into RNA
and eventually proteins
 Biochemistry is all about discovering new biochemical
structures and determining their functions and
interactions with other molecules
 Biochemistry deals with complex molecular machines,
metabolic pathways, and biochemical communications
within and in-between organisms
The Chemical Elements
 Element - simplest form of matter to have unique chemical
properties
 Atomic number of an element - number of protons in its
nucleus
 periodic table
 elements arranged by atomic number
 elements represented by one- or two letter symbols
 24 elements have biological role
 6 elements = 98.5% of body weight
 oxygen, carbon, hydrogen, nitrogen, calcium, and
phosphorus
 trace elements in minute amounts
Atomic Structure
 Nucleus - center of atom
 protons: single + charge, mass = 1 amu (atomic mass unit)
 neutrons: no charge, mass = 1 amu
 Atomic Mass of an element is approximately equal to its total
number of protons and neutrons
 Electrons – in concentric clouds that surround the nucleus
 electrons: single negative charge, very low mass
 determine the chemical properties of an atom
 the atom is electrically neutral because number of electrons is
equal to the number of protons
 valence electrons in the outermost shell
 determine chemical bonding properties of an atom
Isotopes
 Elements are defined by the number of protons in an atom's nucleus
 For example, an atom with 6 protons must be carbon, and an atom with 92
protons must be uranium
 Atoms of the same element can have different numbers of neutrons; the
different possible versions of each element are called isotopes
 For example, the most common isotope of hydrogen has no neutrons at all;
there's also a hydrogen isotope called deuterium, with one neutron, and
another, tritium, with two neutrons.
Electron Energy Shells
 The Bohr Model shows all of
the particles in the atom
 In the center is circles. Each
circle represents a single
neutron or proton
 Protons should have a plus or P
written on them
 Neutrons should be blank or have
an N
 In a circle around the nucleus
are the electrons.
 Electrons should have a minus
sign or an e
 Electrons have special rules that they must follow
 You can’t just shove all of the electrons into the first orbit of an
electron
 Electrons live in something called shells or energy levels.
 Only so many can be in any certain shell.
Nucleus
1st Energy Shell
2nd Energy Shell
3rd Energy Shell
 The electrons in the outer most shell of any element are called
valance electrons
 The electrons that are more loosely held by the nucleus (the valence
electrons, those furthest away from the nucleus) are the ones that are
gained, lost, or shared during chemical reactions
 This is why it is so important to learn and understand about valence
electrons
So let’s try it….
 How to draw a Lithium atom
 First, look at the Periodic Table
 Second, determine the number of
protons (Look @ the atomic
number)
 Then determine the number of
neutrons (Atomic mass – atomic
number)
 Then determine the number of
electrons (Look @ the atomic
number)
3
Li
Lithium
7
So let’s try it….
Protons = 3
3
-
+
+
Li
+
-
-
Lithium
7
Electrons = 3
2 in the 1st shell, 1 in the 2nd shell
Neutrons = 4
(7-3=4)
General Trends of the Periodic Table
 A trend is a pattern or a repetition of
particular properties
 Trends of the periodic table include:

Atomic Mass,
Atomic Radius,
Net Nuclear Charge,
Ion Size,
Metallic or Non-Metallic Property,
Electro-negativity,
1st ionization energy
 The periodic table is arranged in a
certain way to keep elements with
similar properties close together
Groups vs. Periods
 Groups go up and down
 Periods go left and right
 Groups share many similarities
 Periods show periodically (regularly) changing properties
The Alkali Metals
are in Group 1
but Hydrogen is not in this group.
Alkaline Earth Metals
are in Group 2
TRANSITIONAL METALS
are in Groups 3 - 12
INNER
TRANSITIONAL METALS
are at the bottom and fit in as shown
NON-METALS
are at the right hand side of the table
Noble Gases
are at the far right, group 18
First Trend-Atomic Mass
 Atomic mass goes higher from element to element, with few
exceptions
 The Group Trend is that atomic mass increases
 The Period Trend is that atomic mass increases too
 Because of specific properties, the Periodic Table has a non-regular
shape
 The elements are arranged by properties rather than a way just make the table be
uniform in shape
Second Trend-Atom Radius
If you follow along the periodic table for atomic radius, you find:
The Group Trend for atomic radius is that it increases down a group.
The Period Trend for atomic radius is that it decreases left to right.
SHOWS Atomic Sizes for Groups and
Periods
Third Trend-1st Ionization Energy
 1st ionization energy is the amount of energy needed to remove a
valence electron from an entire mole of atoms and make them all into
+1 ions
 For example  To turn a mole of Li atoms into a mole of Li+1 ions, it
would take 520 kJ/mole
FIRST IONIZATION
ENERGY FOR SOME
SELECTED ATOMS
Na
496 kJ/mol
Mg
736 kJ/mol
Al
578 kJ/mol
Si
787 kJ/mol
P
1012 kJ/mol
Going across the 3rd
period, the trend for
1st Ionization Energy
is to INCREASE.
Fourth Trend – Electronegativity
 Electronegativity is the amount of pull that an atom has for another
electron in a bonding situation
 Fluorine has the greatest desire of all atoms for that electron gain
 Fluorine is given the rating of 4.0 on the E-N scale, the highest Electronegativity of all
elements
 Going down a group the trend is towards LOWER E-N values
 Going across a period the trend is towards higher E-N values
 It is all about HOW CLOSE IS THE ATOM TO FLUORINE which determines
the relative electro-negativity.
Exit Quiz
 1). Please illustrate and describe the importance of the typical steps
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that would show up in a flow chart depicting the scientific method.
2). Compare and contrast the differences that exist between mass and
weight in science.
3). What are the three main subatomic particles? Be able to accurately
assign mass, charge and location for each of these subatomic particles.
4). Define atomic number and atomic mass and be prepared to
calculate each value.
5). What is the difference between an electron and a valence electron?
Why are valence electrons so important?
6). What is the difference between ionization energy and
electronegativity? Are there any trends in the periodic table for these
two values? What are they?